Popular explosion models of SNe Ia include the following cases.
(1) The CO WD accretes material from the companion star until its mass nearly reaches the Chandrasekhar mass limit (\(M_{\rm Ch}\) , \(\sim \) 1.4 \(M_{\odot }\) , [1]}) and compressional heating at the center causes the explosion [2]}.
(2) The detonation of a thin layer of He on the surface of a WD [3]}, [4]} triggers a second detonation in the WD center and hence the explosion of a sub-\(M_{\rm Ch}\)  mass C-O WD.
(3) The violent merger or secular merger of two WDs, accompanied by radiation of gravitational waves [5]}, [6]}.
(4) In triple systems, oscillations of the third star cause a direct collision of two WDs and trigger the SN explosion [7]}, [8]}.
In view of these explosion mechanisms, the delayed detonation model is one of the most suitable ones to account for the observed properties of SNe Ia, which initially involves a deflagration of a \(M_{\rm Ch}\)  CO WD and later a supersonic detonation [9]}, [10]}. Nevertheless, the double detonation model of sub-\(M_{\rm Ch}\)  CO WDs shows many striking features, and can also explain the observed properties of some SNe Ia [11]}.
